Biomedical subjects

Georg Nickenig

Publications and source records attributed to Georg Nickenig.

At least 55 records · Page 3Linked to original sources

PubMed2003

Interleukin-6 induces oxidative stress and endothelial dysfunction by overexpression of the angiotensin II type 1 receptor.

Angiotensin II type 1 (AT1) receptor activation as well as proinflammatory cytokines such as interleukin-6 (IL-6) are involved in the development and progression of atherosclerosis. The detailed underlying mechanisms including interactions between inflammatory agonists and the renin-angiotensin system are poorly understood. Stimulation of cultured rat aortic vascular smooth muscle cells (VSMCs) with IL-6 led to upregulation of AT1 receptor mRNA and protein expression, as assessed by Northern and Western blot experiments. Nuclear run-on and transcription blockade experiments showed that IL-6 increases AT1 receptor mRNA de novo synthesis but not mRNA stability. Preincubation of VSMCs with IL-6 resulted in an enhanced angiotensin II-induced production of reactive oxygen species, as assessed by DCF fluorescence laser microscopy. Treatment of C57BL/6J mice with IL-6 for 18 days increased vascular AT1 receptor expression (real-time RT-PCR) and angiotensin II-induced vasoconstriction, enhanced vascular superoxide production (L-012 chemiluminescence, DHE fluorescence), and impaired endothelium-dependent vasodilatation. These effects were completely omitted in AT1 receptor knockout mice (AT1A-/- mice). Upregulation of vascular AT1 receptor expression in vitro and in vivo is decisively involved in IL-6-induced propagation of oxidative stress and endothelial dysfunction. This interaction of the proinflammatory cytokine IL-6 with the renin-angiotensin system may represent an important pathogenetic mechanism in the atherosclerotic process.

Animals↗

PubMed2003

Physical training increases endothelial progenitor cells, inhibits neointima formation, and enhances angiogenesis.

BACKGROUND: The molecular mechanisms by which physical training improves peripheral and coronary artery disease are poorly understood. Bone marrow-derived endothelial progenitor cells (EPCs) are thought to exert beneficial effects on atherosclerosis, angiogenesis, and vascular repair. METHODS AND RESULTS: To study the effect of physical activity on the bone marrow, EPCs were quantified by fluorescence-activated cell sorter analysis in mice randomized to running wheels (5.1+/-0.8 km/d, n=12 to 16 per group) or no running wheel. Numbers of EPCs circulating in the peripheral blood of trained mice were enhanced to 267+/-19%, 289+/-22%, and 280+/-25% of control levels after 7, 14, and 28 days, respectively, accompanied by a similar increase of EPCs in the bone marrow and EPCs expanded from spleen-derived mononuclear cells. eNOS-/- mice and wild-type mice treated with N(G)-nitro-l-arginine methyl ester showed lower EPC numbers at baseline and a significantly attenuated increase of EPC in response to physical activity. Exercise NO dependently increased serum levels of vascular endothelial growth factor and reduced the rate of apoptosis in spleen-derived EPCs. Running inhibited neointima formation after carotid artery injury by 22+/-2%. Neoangiogenesis, as assessed in a subcutaneous disc model, was increased by 41+/-16% compared with controls. In patients with stable coronary artery disease (n=19), moderate exercise training for 28 days led to a significant increase in circulating EPCs and reduced EPC apoptosis. CONCLUSIONS: Physical activity increases the production and circulating numbers of EPCs via a partially NO-dependent, antiapoptotic effect that could potentially underlie exercise-related beneficial effects on cardiovascular diseases.

Aged↗

PubMed2003

Addition of paclitaxel to contrast media prevents restenosis after coronary stent implantation.

OBJECTIVES: The present study was designed to test the efficacy of paclitaxel added to the contrast agent iopromide in the prevention of restenosis. BACKGROUND: Contrast media adhere to the coronary vessel wall for some seconds after injection. Such a layer of contrast agent could serve as a matrix for antiproliferative drugs. METHODS: Thirty-four stents were implanted into the left anterior descending and circumflex coronary arteries of 17 pigs, using a 1.2:1.0 overstretch ratio. The unsupplemented contrast agent iopromide-370 was used as a control; the treatment groups were treated with 80 ml intracoronary iopromide plus either 100 or 200 mumol/l paclitaxel, or 80 ml intravenous iopromide plus 200 mumol/l paclitaxel. Quantitative angiography and histomorphometry were used to assess comparable baseline parameters between the treatment groups. RESULTS: A short time incubation (3 min) almost completely inhibited vascular smooth muscle cell proliferation, sustained for up to 12 days. Whereas intravenous paclitaxel had no effect, intracoronary application of paclitaxel reduced the diameter stenosis from 55 +/- 13% to 29 +/- 18% and 13 +/- 12%. Late lumen loss dropped from 1.94 +/- 0.35 mm under the control condition to 1.19 +/- 0.55 mm with 100 mumol/l paclitaxel and to 0.82 +/- 0.54 mm with 200 mumol/l paclitaxel. Histomorphometry revealed a corresponding dose-dependent reduction of the neointimal area and restenosis by intracoronary iopromide paclitaxel. Assessment of left ventricular function and myocardial histology revealed no adverse effects of intracoronary paclitaxel application. CONCLUSIONS: This study provides evidence that intracoronary application of a taxane dissolved in a contrast medium profoundly inhibits in-stent restenosis. This novel, widely feasible approach may be suited for the prevention of restenosis in a broad spectrum of interventional treatment regimens.

Animals↗

PubMed2003

Rapid effect of 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibition on coronary endothelial function.

Treatment with 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) decreases cardiovascular event rates in hypercholesterolemic patients. Whether statins exert effects within 24 hours on the coronary vasculature in patients with endothelial dysfunction has not been elucidated. Twenty-seven patients with stable angina pectoris and average low-density lipoprotein cholesterol concentrations of 138+/-9 mg/dL at baseline were allocated to treatment with placebo (14 patients) or 40 mg/d pravastatin (13 patients) in a randomized, double-blind, prospective trial. Coronary endothelial function was assessed before and 24 hours after single treatment by quantitative coronary angiography during intracoronary infusion of nitroglycerin or increasing concentrations of acetylcholine (0.01, 0.1, and 1 micromol/L). Coronary blood flow reserve was measured by Doppler velocimetry during adenosine infusion. Intracoronary acetylcholine infusion induced abnormal vasoconstriction in both groups before treatment, indicating coronary endothelial dysfunction. Treatment with a single oral 40-mg dose of pravastatin significantly attenuated acetylcholine-mediated vasoconstriction after 24 hours (mean+/-SE decrease in luminal diameter before and after treatment: 0.01 micromol/L, 6.1+/-2.2% versus 3.0+/-1.2%; 0.1 micromol/L, 15.6+/-2.6% versus 7.4+/-1.8%; P<0.05; 1 micromol/L, 22.9+/-2.9% versus 13.2+/-2.6%; P<0.05). There was no significant difference in the response to acetylcholine in the placebo group (8.1+/-2.4% versus 9.7+/-2.4%, 16.1+/-2.9% versus 16.8+/-3.2%, and 21.4+/-3.9% versus 23.3+/-4.2%). The response to nitroglycerin infusion was not altered in both groups. Increase in coronary blood flow in response to adenosine and coronary flow reserve remained unchanged during placebo and statin treatment. Serum concentrations of blood lipids and high-sensitive C-reactive protein were not significantly altered after 24 hours in response to placebo or pravastatin therapy. Statin treatment improves endothelium-dependent coronary vasomotion within 24 hours in the absence of significant cholesterol reduction. The full text of this article is available online at http://www.circresaha.org.

Aged↗

PubMed2003

Oxygen free radical release in human failing myocardium is associated with increased activity of rac1-GTPase and represents a target for statin treatment.

BACKGROUND: Reactive oxygen species (ROS) contribute to the development of heart failure. A potential source of myocardial ROS is the NADPH oxidase, which is regulated by the small GTP-binding protein rac1. Isoprenylation of rac1 can be inhibited by statin therapy. Thus, we examined ROS and rac1 in human failing myocardium and tested their regulation by statins in vivo. METHODS AND RESULTS: In human left ventricular myocardium from patients with ischemic cardiomyopathy (ICM) or dilated cardiomyopathy (DCM), NADPH oxidase activity was increased 1.5-fold compared with nonfailing controls (P<0.05, n=8). In failing myocardium, increased oxidative stress determined by measurements of lipid peroxidation and aconitase activity was associated with increased translocation of rac1 from the cytosol to the membrane. Pull-down assays revealed a 3-fold increase of rac1-GTPase activity in ICM and DCM. In parallel, membrane expression of the NADPH oxidase subunit p47phox, but not p67phox, was upregulated in failing compared with nonfailing myocardium. In right atrial myocardium from patients undergoing cardiac surgery who were prospectively treated with atorvastatin or pravastatin (40 mg/d, 4 weeks), rac1-GTPase activity was decreased to 67.9+/-12% and 65.6+/-13.8% compared with patients without statin (P<0.05, n=8). Both atorvastatin and pravastatin significantly reduced angiotensin II-stimulated but not basal NADPH oxidase activity. CONCLUSIONS: Failing myocardium of patients with DCM and ICM is characterized by upregulation of NADPH oxidase-mediated ROS release associated with increased rac1 activity. Oral statin treatment inhibits myocardial rac1-GTPase activity. These data suggest that extrahepatic effects of statins can be observed in humans and may be beneficial for patients with chronic heart failure.

Cardiac Output, Low↗

PubMed2003

Beneficial effects of immediate stenting after thrombolysis in acute myocardial infarction.

OBJECTIVES: The Southwest German Interventional Study in Acute Myocardial Infarction (SIAM III) investigated potentially beneficial effects of immediate stenting after thrombolysis as opposed to a more conservative treatment regimen. BACKGROUND: Treatment of acute myocardial infarction (AMI) by thrombolysis is compromised by Thrombolysis In Myocardial Infarction (TIMI) 3 flow rates of only 60% and high re-occlusion rates of the infarct-related artery (IRA). Older studies showed no benefit of coronary angioplasty after thrombolysis compared with thrombolytic therapy alone. This observation has been challenged by the superiority of primary stenting over balloon angioplasty in AMI. METHODS: The SIAM III study was a multicenter, randomized, prospective, controlled trial in patients receiving thrombolysis in AMI (<12 h). Patients of group I were transferred within 6 h after thrombolysis for coronary angiography, including stenting of the IRA. Group II received elective coronary angiography two weeks after thrombolysis with stenting of the IRA. RESULTS: A total of 197 patients were randomized, 163 patients fulfilled the secondary (angiographic) inclusion criteria (82 in group I, 81 in group II). Immediate stenting was associated with a significant reduction of the combined end point after six months (ischemic events, death, reinfarction, target lesion revascularization 25.6% vs. 50.6%, p = 0.001). CONCLUSIONS: Immediate stenting after thrombolysis leads to a significant reduction of cardiac events compared with a more conservative approach including delayed stenting after two weeks.

Aged↗

PubMed2003

Intravenous transfusion of endothelial progenitor cells reduces neointima formation after vascular injury.

Endothelial cell damage is one important pathophysiological step of atherosclerosis and restenosis after angioplasty. Accelerated reendothelialization impairs neointima formation. We evaluated the role of intravenously transfused endothelial progenitor cells (EPCs) on reendothelialization and neointima formation in a mouse model of arterial injury. Spleen-derived mouse mononuclear cells (MNCs) were cultured in endothelial basal medium. A total of 91.8+/-3.2% of adherent cells showed uptake of acetylated low-density lipoprotein (Dil-Ac-LDL) and lectin binding after 4 days. Immunostaining and long-term cultures confirmed the endothelial progenitor phenotype. To determine the effect of stem cell transfusion on reendothelialization, mice received either fluorescent-labeled spleen-derived MNCs or in vitro differentiated EPCs intravenously after endothelial injury of the carotid artery. Transfused cells were strictly restricted to the injury site, and lectin binding confirmed the endothelial phenotype. Homing of transfused cells to the site of injury was only detectable in splenectomized mice. Cell transfusion caused enhanced reendothelialization associated with a reduction of neointima formation. Systemically applied spleen-derived MNCs and EPCs home to the site of vascular injury, resulting in an enhanced reendothelialization associated with decreased neointima formation. These results allow novel insights in stem cell biology and provide additional information for the treatment of vascular dysfunction and prevention of restenosis after angioplasty. The full text of this article is available online at http://www.circresaha.org.

Animals↗

PubMed2003

Modulation of antioxidant enzyme expression and function by estrogen.

Oxidative stress plays a pivotal role in the pathogenesis of atherosclerosis and can be effectively influenced by radical scavenging enzyme activity and expression. The vasoprotective effects of estrogens may be related to antioxidative properties. Therefore, effects of 17beta-estradiol on production of reactive oxygen species and radical scavenging enzymes were investigated. 17beta-estradiol diminished angiotensin II-induced free radical production in vascular smooth muscle cells (DCF fluorescence laser microscopy). 17beta-estradiol time- and concentration-dependently upregulated manganese (MnSOD) and extracellular superoxide dismutase (ecSOD) expression (Northern and Western blotting) and enzyme activity (photometric assay). Nuclear run-on assays demonstrated that 17beta-estradiol increases MnSOD and ecSOD transcription rate. Half-life of MnSOD mRNA was not influenced, whereas ecSOD mRNA was stabilized by estrogen. Copper-zinc SOD, glutathione-peroxidase, and catalase were not affected by estrogen. Estrogen deficiency in ovariectomized mice induced a downregulation of ecSOD and MnSOD expression, which was associated with increased production of vascular free radicals and prevented by estrogen replacement or treatment with PEG-SOD. In humans, increased estrogen levels led to enhanced ecSOD and MnSOD expression in circulating monocytes. Estrogen acts antioxidative at least to some extent via stimulation of MnSOD and ecSOD expression and activity, which may contribute to its vasoprotective effects.

Angiotensin II↗

PubMed2003

Estrogen increases bone marrow-derived endothelial progenitor cell production and diminishes neointima formation.

BACKGROUND: Estrogens improve endothelial function and accelerate reendothelialization after vascular injury via largely unknown mechanisms. Bone marrow-derived endothelial progenitor cells (EPCs) are thought to positively influence endothelialization, vascular repair, and angiogenesis. METHODS AND RESULTS: In mice subjected to sham operation, ovariectomy, or ovariectomy and estrogen replacement treatment, estrogen deficiency significantly decreased EPCs circulating in the peripheral blood and residing in the bone marrow, as well as EPCs that were in vitro expanded from spleen-derived mononuclear cells. These effects were completely prevented by estrogen replacement. Human women with increased estrogen plasma concentrations also displayed profoundly increased levels of circulating EPCs. Estrogens increase EPC numbers through a decreased apoptosis rate, which is mediated via a caspase-8-dependent pathway. Estrogen deficiency increased neointima formation after carotid artery injury in mice, but this effect was diminished by estrogen replacement therapy. In mice transplanted with green fluorescent protein-positive bone marrow, reendothelialization of injured vessel segments by bone marrow-derived cells was decreased during estrogen deficiency and increased in response to estrogen treatment. CONCLUSIONS: Estrogens increase numbers of EPCs by antiapoptotic effects leading to accelerated vascular repair and decreased neointima formation.

Animals↗

PubMed2003

Mechanisms of stroke protection by physical activity.

Regular physical activity is associated with a decrease of cerebrovascular and cardiovascular events, which may relate to enhanced endothelium-dependent vasodilation. Here, we provide evidence that physical activity protects against ischemic stroke via mechanisms related to the upregulation of endothelial nitric oxide synthase (eNOS) in the vasculature. Voluntary training on running wheels or exercise on a treadmill apparatus for 3 weeks, respectively, reduced cerebral infarct size and functional deficits, improved endothelium-dependent vasorelaxation, and augmented cerebral blood flow in wild-type mice. The neuroprotective effects of physical training were completely absent in eNOS-deficient mice, indicating that the enhanced eNOS activity by physical training was the predominant mechanism by which this modality protects against cerebral injury. Our results suggest that physical activity not only decreases stroke risk, but also provides a prophylactic treatment strategy for increasing blood flow and reducing brain injury during cerebral ischemia.

Animals↗

PubMed2003

Interrelationship of free oxygen radicals and endothelial dysfunction--modulation by statins.

3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are successfully used for the treatment of hypercholesterolemia and profoundly reduce cardiovascular morbidity and mortality in hypercholesterolemic patients. Endothelial dysfunction is the early state of atherosclerosis and predicts adverse cardiac events and mortality. Reduced nitric oxide (NO) bioactivity in the vascular wall, caused by increased free oxygen-radical generation and decreased NO production, seems to be an important underlying mechanism. It is well established that statins improve endothelial dysfunction in hypercholesterolemic patients. However, results from in vitro studies, animal experiments, and small clinical trials suggest that statins may improve vascular function after short-term treatment in hyper- and normocholesterolemic individuals. The underlying mechanisms may at least in part be related to the cholesterol-independent effects of statins on vascular cells. Cellular antioxidative properties of statins, leading to decreased oxidative stress and restoration of NO bioactivity, may be of special relevance for the improvement of vascular function. However, further studies and clinical intervention trials are required to clarify the clinical importance of the pleiotropic effects in humans and their contribution to the well-established clinical benefits of statins and to confirm a beneficial effect of statin therapy on endothelial dysfunction and cardiovascular events in normocholesterolemic patients.

Animals↗

PubMed2003

Withdrawal of statin treatment abrogates stroke protection in mice.

BACKGROUND AND PURPOSE: Statins (3-hydroxy-3-methylglutaryl-coenzyme A [HMG-CoA] reductase inhibitors) reduce stroke damage independent of lipid lowering by upregulation of endothelial nitric oxide synthase (eNOS). Acute withdrawal of statin treatment may suppress endothelial NO production and impair vascular function. METHODS: To test this hypothesis, we treated 129/SV mice with atorvastatin (10 mg/kg) for 14 days and then withdrew treatment. RESULTS: Treatment with atorvastatin conferred stroke protection by 40% after filamentous occlusion of the middle cerebral artery followed by reperfusion. Withdrawal of statin treatment, however, resulted in the loss of stroke protection after 2 and 4 days. In mouse aortas and brain vasculature, statins upregulated eNOS message 2.3- and 1.7-fold, respectively, as measured by reverse transcription-polymerase chain reaction. Withdrawal of statins resulted in 5- and 2.7-fold downregulation of eNOS in aorta and brain, respectively, after 2 days. Statin treatment decreased RhoA GTPase membrane expression to 48%, while withdrawal of statins resulted in 4-fold increase of RhoA in the membrane. Moreover, platelet factor 4 and beta-thromboglobulin in plasma were significantly downregulated by statin treatment, but withdrawal of statins resulted in a 2.9- and 3.1-fold upregulation after 2 days, respectively. Thrombus formation induced by ligature of the inferior vena cava was significantly reduced by statin treatment. When statin treatment was withdrawn, however, protection was lost between 2 and 4 days. CONCLUSIONS: Acute termination of statin treatment results in a rapid loss of protection in mouse models of cerebral ischemia and thrombus formation independent of lipid lowering. In patients with acute or impending stroke, withdrawal of statins may impair outcome.

Animals↗

PubMed2003

[Exercise training in heart failure].

BACKGROUND: In patients with chronic heart failure, exercise limitation cannot be exclusively attributed to cardiac dysfunction. During progression of the disease, peripheral factors have a growing impact on functional capacity. Chronic underperfusion of skeletal muscles, inactivity and a harmful effect of neuroendocrine stimulation lead to a myopathy syndrome characterized by atrophy, a shift in muscle fiber type and a loss of capillaries and mitochondria, which cause reduced muscle strength and aerobic capacity. Unlike left ventricular systolic function, which is a poor predictor of exercise tolerance in patients with chronic heart failure, parameters characterizing the myopathy syndrome correlate well with functional capacity. In the last 20 years, numerous studies have demonstrated that chronic heart failure patients in NYHA classes II and III benefit from physical training without deterioration of their cardiac function. EFFECTS OF EXERCISE TRAINING: Physical activity primarily improves muscle function and increases maximal as well as submaximal exercise capacity. Advantageous effects have also been observed with regard to neuroendocrine stimulation. The effect on central hemodynamics is much smaller and indirectly mediated by a trend towards decreased peripheral resistance. Left ventricular diameters, ejection fraction and filling pressures do not show significant changes. The gain in exercise capacity is usually accompanied by an improvement in symptom status and quality of life. Recent studies indicate that prognosis may also be improved by exercise training. CONVERSION INTO CLINICAL PRACTICE: Although continuous exercise training (mainly by use of cycle ergometry) has been investigated most thoroughly, there is an increasing number of studies reporting beneficial effects of interval and resistance training. Before starting a standardized training program, functional limitation and training intensity should be determined by an appropriate stress test. During the first training sessions, patients should always be supervised by a physician. In order to increase efficiency and feasibility of the exercise therapy, home-based training should be engaged as soon as a stable condition during repeated training sessions has been proven.

Chronic Disease↗

PubMed2002

Down-regulation of Rac-1 GTPase by Estrogen.

Rac1 GTPase is essential for the activation of the NAD(P)H oxidase complex and, thereby, regulates the release of reactive oxygen species (ROS) in the vessel wall. 17 beta-estradiol (E2) inhibits vascular ROS production. To elucidate the underlying molecular mechanisms we investigated the potential regulation of Rac1 by E2 in vascular smooth muscle cells. Treatment of vascular smooth muscle cells with angiotensin II as well as overexpression of the constitutively active mutant RacL61 increased ROS release as assessed by dichlorofluorescein fluorescence, whereas inhibition of Rac1 by Clostridium sordellii lethal toxin or overexpression of dominant-negative RacN17 inhibited ROS production. Treatment with E2 (100 nm) completely prevented angiotensin II-induced NAD(P)H oxidase activity and ROS production. E2 time and concentration dependently decreased angiotensin II-induced and basal Rac1 mRNA and protein expression as well as Rac1 activity. Down-regulation of Rac1 expression by E2 was mediated by inhibition of gene transcription (nuclear run-on assays), but E2 had no effect on Rac1 mRNA stability. Regulation of Rac1 was mediated by estrogen receptors since co-incubation with ICI 182.780 prevented down-regulation of Rac1. To test these observations in vivo, ovariectomized spontaneously hypertensive rats were treated with E2 or vehicle. Real-time PCR and Western blotting showed reduction of aortic Rac1 mRNA and protein by 32 and 58%, respectively. Furthermore, down-regulation of Rac1 by E2 was observed in human mononuclear cells of women with elevated E2 levels after controlled ovarian hyperstimulation. Rac1 GTPase gene-transcription and activity is regulated by 17 beta-estradiol, which may be an important molecular mechanism contributing to the cardiovascular effects of estrogens.

Angiotensin II↗

PubMed2002

Bone marrow-derived progenitor cells modulate vascular reendothelialization and neointimal formation: effect of 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibition.

OBJECTIVE: Atherosclerosis and restenosis after vascular injury are both characterized by endothelial dysfunction, apoptosis, inappropriate endothelialization, and neointimal formation. Bone marrow-derived endothelial progenitor cells have been implicated in neovascularization, resulting in adult blood vessel formation. Despite the anticipated stem cell plasticity, the role of bone marrow-derived endothelial progenitor cells has not been clarified in vascular lesion development. METHODS AND RESULTS: We investigated vascular lesion formation in mice after transplantation of bone marrow transfected by means of retrovirus with enhanced green fluorescent protein. Carotid artery injury was induced, resulting in neointimal formation. Fluorescence microscopy and immunohistological analysis revealed that bone marrow-derived progenitor cells are involved in reendothelialization of the vascular lesions. Treatment with rosuvastatin (20 mg/kg body wt per day), a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, enhanced the circulating pool of endothelial progenitor cells, propagated the advent of bone marrow-derived endothelial cells in the injured vessel wall, and, thereby, accelerated reendothelialization and significantly decreased neointimal formation. CONCLUSIONS: Vascular lesion development initiated by endothelial cell damage is moderated by bone marrow-derived progenitor cells. 3-Hydroxy-3-methylglutaryl coenzyme A reductase inhibition promotes bone marrow-dependent reendothelialization and diminishes vascular lesion development. These findings may help to establish novel pathophysiological concepts and therapeutic strategies in the treatment of various cardiovascular diseases.

Animals↗

PubMed2002

Angiotensin II type 1 receptor antagonism improves hypercholesterolemia-associated endothelial dysfunction.

OBJECTIVE: Hypercholesterolemia-induced angiotensin II type 1 (AT1) receptor overexpression is thought to be a key event in the development of endothelial dysfunction. METHODS AND RESULTS: The effect of a 6-week treatment with the AT1 receptor antagonist candesartan (16 mg/d) on endothelial function and serum inflammation markers was compared with the effect of treatment with placebo or the calcium channel antagonist felodipine (5 mg/d) in 47 hypercholesterolemic patients (low density lipoprotein cholesterol >160 mg/dL). Endothelial function was assessed by measurement of forearm blood flow (FBF) by venous occlusion plethysmography. FBF during reactive hyperemia was significantly improved by candesartan, whereas felodipine and placebo exerted no effect. Nitroglycerin-induced vasorelaxation and basal FBF were not altered significantly. Blood pressure and cholesterol levels were not affected significantly by any drug. Serum concentrations of 8-isoprostane, monocyte chemoattractant protein-1, and soluble intercellular adhesion molecule-1 were significantly reduced by candesartan treatment but not by placebo or felodipine (ELISA assays). Levels of high-sensitivity C-reactive protein and tumor necrosis factor-alpha were not altered significantly by any treatment. CONCLUSIONS: These data suggest that AT1 receptor antagonism improves endothelial function during hypercholesterolemia and that this applies not only to endothelium-dependent vasodilatation but also to oxidative stress and events involved in monocyte attraction and adhesion. AT1 receptor blockade may potentially represent a novel approach for the prevention of vascular dysfunction associated with hypercholesterolemia that is independent of lipid-lowering and blood pressure-lowering interventions.

Angiotensin II↗

PubMed2002

Rosuvastatin, a new HMG-CoA reductase inhibitor, upregulates endothelial nitric oxide synthase and protects from ischemic stroke in mice.

HMG-CoA reductase inhibitors (statins) are cholesterol-lowering drugs and reduce the risk of myocardial infarction and stroke. In this study we investigated whether rosuvastatin, a new, potent HMG-CoA reductase inhibitor, upregulates endothelial nitric oxide (NO) expression and activity and protects from cerebral ischaemia in mice. Endothelial cells in culture and 129/SV mice were chronically treated with rosuvastatin. The expression and activity of endothelial NO synthase (eNOS) was determined by reverse-transcriptase polymerase chain reaction (RT-PCR), Western blotting and arginine-citrulline assays. Cerebral ischaemia was induced by occlusion of the middle cerebral artery (MCAo) for 2 h and infarct size was determined after 22 h of reperfusion. Treatment of endothelial cells with rosuvastatin concentration- and time-dependently upregulated eNOS mRNA and protein expression. In aortas of 129/SV wild-type mice, treatment with 0.2, 2, and 20 mg kg(-1) rosuvastatin subcutaneously (s.c.) for 10 days significantly upregulated eNOS mRNA by 50, 142, and 205%, respectively. NOS activity was significantly increased by 75, 145, and 320%, respectively. Stroke volume after 2-h MCAo was reduced by 27, 56, and 50% (for 0.2, 2 and 20 mg kg(-1), respectively). Serum cholesterol and triglygeride levels were not significantly lowered by the treatment. The novel HMG-CoA reductase inhibitor rosuvastatin dose-dependently upregulates eNOS expression and activity and protects from cerebral ischaemia in mice. The effects are independent of changes in cholesterol levels and are equivalent or even superior to the protective effects by simvastatin and atorvastatin in this animal model.

Animals↗

PubMed2002

Identification of a novel redox-sensitive gene, Id3, which mediates angiotensin II-induced cell growth.

BACKGROUND: Reactive oxygen species, such as superoxide (O(2)(-)), are involved in the abnormal growth of various cell types. Angiotensin II (Ang II) is one of the most potent inducers of oxidative stress in the vasculature. The molecular events involved in Ang II-induced proliferation of vascular smooth muscle cells (VSMCs) are only partially understood. METHODS AND RESULTS: Ang II as well as xanthine/xanthine oxidase (X/XO) led to enhanced DNA synthesis and proliferation of VSMCs. The effect of Ang II was abolished by diphenylene iodonium. Consequently, VSMCs were incubated with X/XO, and modulation of gene expression was monitored by differential display, leading to the identification of a novel redox-sensitive gene, the dominant-negative helix-loop-helix protein Id3, which was upregulated within 30 minutes by X/XO and Ang II. Superoxide dismutase but not catalase inhibited this effect. Overexpression of antisense Id3 via transfection in VSMCs completely abolished Ang II- and X/XO-induced cell proliferation. Ang II, X/XO, and overexpression of sense Id3 downregulated protein expression of p21(WAF1/Cip1), p27(Kip1), and p53. Overexpression of antisense Id3 abrogated the effect of Ang II on the expression of p21(WAF1/Cip1), p27(Kip1), and p53. Ang II and overexpression of sense Id3 caused hyperphosphorylation of the retinoblastoma protein. Ang II-induced phosphorylation of the retinoblastoma protein was decreased by overexpression of antisense Id3. CONCLUSIONS: Ang II induces proliferation of VSMCs via production of superoxide, which enhances the expression of Id3. Id3 governs the downstream mitogenic processing via depression of p21(WAF1/Cip1), p27(Kip1), and p53. These findings reveal a novel redox-sensitive pathway involved in growth control.

Angiotensin II↗